C++控制结构学习笔记二

"条件结构（if and else）;
例一：
if (x == 100) {
cout << ""x is 100。\n"";
} else {
cout << ""x is not 100。"";
}
例二：
if (x > 0)
cout << ""x is positive。\n"";
else if (x < 0)
cout << ""x is negative。\n"";
else
cout << ""x is 0.""; "

"循环结构；
while循环，例一：
#include <iostream.h>
int main() {
int n;
cout << ""Enter the starting number"";
cin >> n;
while (n > 0) {
cout << n << "","";
--n;
}
cout << ""FIRE！"";
return 0;
}
do - while循环，例二：
#include <iostream.h>
int main() {
ussigned long n;
do {
cout << ""Enter number (0 to end):"";
cin >> n;
cout << ""You entered:"" << n << ""\n"";
} while (n != 0);
return 0;
}
for 循环，例三：
#include <iostream.h>
int main() {
for (int n=10; n>0; n--) {
cout <<ｎ << "","";
}
cout << ""FIRE！"";
return 0;
}
"
"分支控制和跳转；
break语句，在满足条件下强制跳出循环，例四：
#include <iostream.h>
int main() {
int n;
for (n=10; n > 0;; n--) {
cout << n << "","";
if (n == 3) {
cout << ""countdown aborter！"";
break;
}
}
return 0;
}
输出结果：10, 9, 8, 7, 6, 5, 4, 3, countdown aborted!
continue语句，跳出当前循环，直接进入下次循环，例五：
#include <iostream.h>
int main() {
for (int n =10; n > 0; n--) {
if (n == 5) continue;
cout << n << "","";
}
cout << ""FIRE！"";
return 0;
}
输出结果：10, 9, 8, 7, 6, 4, 3, 2, 1, FIRE!
goto 语句，可以从程序一点跳到另外一点，goto语句参数是由表示名加冒号组成，例六：
#include <iostream.h>
int main() {
int n = 10;
loop:
cout << n << "","";
n--;
if (n > 0) goto loop;
cout << ""FIRE！"";
return 0;
}
输出结果：10, 9, 8, 7, 6, 5, 4, 3, 2, 1, FIRE! "
"选择结构；
switch (x) {
case 1:
cout << ""x is 1。"";
break;
case 2:
cout << ""x is 2。"";
break;
default:
cout << ""value of x unknown。"";
}
注意：每个分支后面必须包含break语句，只能用来比较表达式或不同常量的值，不能把变量或范围放在case之后。"